【作者】 胡华锋；

【导师】 李有田； 介晓磊；

【作者基本信息】 河南农业大学 ， 土壤学， 2004， 硕士

【摘要】 采用间歇法(batch methods),模拟研究土壤中几种低分子量有机酸(Low-molecular-weight organic acids,简称 LOAs) (柠檬酸，草酸，苹果酸)对红壤区主要粘土矿物-高岭石的溶解作用及盐基离子的活化作用，结果表明：1) LOAs 对高岭石的溶解能力随有机酸浓度的增加及酸度的升高而 增强。且一般情况下，其对高岭石的溶解能力都大于质子(HAC)对 高岭石的溶解能力。2) 在不调节酸度的情况下，有机酸对高岭石的溶解能力顺序为：草 酸>柠檬酸>苹果酸；而在HAC/NH4AC 缓冲溶液体系中，有机酸对 高岭石的溶解能力既与其浓度有关又与其酸度有关，当有机酸浓度 为 1mM， pH3.5 时，草酸>柠檬酸>苹果酸；pH5.5 和 pH4.5 时， 柠檬酸>草酸>苹果酸；而当有机酸浓度≥5mM 时,草酸>柠檬酸>苹 果酸。3) 不调节酸度的苹果酸导致了高岭石 Si 的优先释放，而在 HAC/NH4AC 缓冲溶液体系中，苹果酸却导致了 Al 的优先释放， 然而，对于柠檬酸和草酸而言，无论是否调节其酸度，都导致了 Al 的优先释放。对于柠檬酸和草酸而言，一般情况下，高岭石是 在反应中期或后期才趋于同步溶解；而对于苹果酸而言，高岭石溶 解同步性较为复杂。4) 有机酸能促进高岭石中 K+、Na+、Ca2+、Mg2+等盐基离子的释放， 甚至在较低的浓度(100μM)。但其对高岭石盐基离子的释放影响较 复杂。5) HAC 作用下，高岭石的反应级数(nH)和速率常数(kH)分别为 0.28 和 1.12×10-12；当柠檬酸、草酸和苹果酸浓度为 1mM 时，反应级数 (nH )分别为 0.09、0.27 和 0.18，速率常数(kH )分别为 4.03×10-13、 L L 2.62×10-12和 4.73×10-13；当其浓度为 5mM 时，其反应级数(nH )分 L 1<WP=10>低分子量有机酸对高岭石溶解作用的研究 别为 0.16、0.37 和 0.16，速率常数(kH )分别为 1.38×10-12、2.32×10-11 L 和 4.97×10-13；其浓度为 10mM 时，反应级数(nH )分别为 0.18、0.34 L 和 0.16，速率常数(kH )分别为 2.17×10-12、2.60×10-11和 6.05×10-13。 L6) 配体对高岭石的溶解能力既受反应液酸度影响又受有机酸类型的 影响。柠檬酸作用下，当其浓度>1mM 时，反应液中酸度的增加有 利于配体对高岭石溶解能力的提高，而当其浓度≤1mM 时，酸度 的增加可能有抑制配体对高岭石的溶解能力。草酸作用下，酸度的 增加也有利配体对高岭石的溶解能力的提高。但苹果酸作用下，当 其浓度为 10mM 时，反应液中酸度的增加有利于配体对高岭石溶解 能力的提高，而当其浓度为 1mM 和 5mM 时，酸度的增加却可能 有抑制配体对高岭石的溶解能力。对于柠檬酸和草酸而言，在促进 高岭石溶解的作用上，配体的贡献是主要的；而对于苹果酸而言， 在促进高岭石溶解的作用上，配体的贡献是次要的。7) 配体促进溶解速率(RL)可以用配体浓度的指数形式来表示。对柠檬 酸、草酸和苹果酸而言，pH5.5 时，分别为 RL=10-13.01[配体]0.23、 RL=10-13.28[配体]0.70 和 RL=10-13.72[配体]0.38；pH4.5 时，分别为 RL=10-13.00[配体]0.51、RL=10-13.03[配体]1.05 和 RL=10-14.07[配体]0.77； pH3.5 时，分别为 RL=10-12.99[配体]0.64、RL=10-12.72[配体]0.89 和 RL=10-14.61[配体]1.69。更多还原

【Abstract】 In order to know better the effect of low -molecular -weightorganic acid (LOAs) in soils in the processes of red soil acidification, the experimentwas conducted to evaluate the role of several kinds of LOAs ( citiric acid, oxalic acidand malic acid) on the dissolution and base cation activation of kaolinite with batchmethod. The result showed as follows:1) Solvability of kaolinite was enhanced with an increase in the concentration and acidity of LOAs. Moreover in general, the solvability of LOAs on kaolinite were biggerthan proton (HAC).2) When the acidity of LOAs wasn’t adjusted, LOAs promoted the kaolinite solvability in the order oxalic acid > citric acid > malic aicd; However in HAC/NH4AC buffer solution, the ability that LOAs promoted the kaolinite dissolution had relation to the concentration and acidity of LOAs, when the concentration of LOAs was 1mM, LOAs promoted the kaolinite solvability in the order oxalic acid > citric acid > malic aicd (pH3.5) and citric acid > oxalic acid > malic acid (pH4.5 and pH5.5 ); However, when the concentration of LOAs was as big as or bigger than 5mM, the order was oxalic acid >citric acid >malic aicd.3) When the acidity of malic acid wasn’t adjusted, Si was preferentially released compared to Al, but in HAC/NH4AC buffer solution, the malic acid resulted in the preferential release of Al; However in respect of citric acid and oxalic acid, no matter if the acidity was adjusted, Al was both preferentially released compared to Si. In general, in citric acid and oxalic acid solution, kaolinite nearly dissolved congruently in reactive metaphase or anaphase; In malic acid solution, stoichiometry of kaolinite dissolution is complex. 117<WP=126>低分子量有机酸对高岭石溶解作用的研究4) LOAs could promote the release of K+, Na+, Ca2+, Mg2+ from kaolinite, even if the concentration of LOAs was very low (100μM). But the effect of the concentration of LOAs on the release of base cation from kaolinite was complex.5) The reaction order(nH) and rate constant(kH) of kaolinite dissolution in HAC/NH4AC buffer solution were 0.28 and 1.12×10-12 respectively; when the concentration of citric acid , oxalic acid and malic acid was 1mM. The reaction order(nH ) were 0.09, 0.27 and 0.18 respectively，the rate constant (kH ) were L L 4.03×10-13, 2.62×10-12 and 4.73×10-13 respectively；when the concentration was 5mM, The reaction order(nH ) were 0.16, 0.37 and 0.16 respectively，the rate L constant (kH ) were 1.38×10-12, 2.32×10-11 and 4.97×10-13 respectively； when L the concentration was 10mM, The reaction order(nH ) were 0.18, 0.34 and 0.16 L respectively，the rate constant (kH ) were 2.17×10-12, 2.60×10-11 and 6.05×10-13 L respectively.6) The ability of Ligand-promoted kaolinite dissolution was related to reactive solution acidity and the kind of LOAs. In citric acid solution, when the concentration of citric acid was bigger than 1mM, the enhance of solution acidity availed the increase of Ligand-promoted kaolinite dissolution,however when the concentration of citric acid was no more than 1mM, the enhance of solution acidity possibly restrained the ability of Ligand-promoted kaolinite dissolution. In oxalic acid solution, the enhance of solution acidity availed the increase of Ligand-promoted kaolinite dissolution. But In malic acid solution, when the concentration of malic acid was 10mM, the enhance of solution acidity availed the increase of Ligand-promoted kaolinite dissolution, however when the concentration of malic acid was 1mM and 5mM, the enhance of solution acidity possibly restrained the ability of Ligand-promoted kaolinite dissolution. Ho更多还原